Lots of interesting observations in this thread. My experience with Gatorskins began in 2007-ish, when I tired of so many flats. Nothing could be more anecdotal than my remarks. I've ridden roughly 30,000km on them, beginning with 23mm, then 25mm, now 28mm. They are on my Ti commuter/road bike (my commute is 53km each way, so I commute on a road bike). In addition to the commute, I do lots of 120km+ rides, much of that in the Rockies, so plenty of descents at speeds of 70km/h+. So far I have not found them to be unpleasantly rough riding, nor hair-raising in the high speed bends. Like many things in life, I think that your perspective will be influenced by what else you have tried.
I run Conti GP5000s on my tri bike (carbon Kestrel), and used to run Vittoria Corsa whatevers. Convinced that the rolling resistance difference was noticeable, I've tried swapping wheels between bikes (which is another variable not controlled for, of course), and it was apparent that the Gatorskins don't provide the same road feel, and are higher resistance. I can't speak to the grip, since I haven't ever found myself skidding out of control on either.
I've only had a couple of flats since I began using them, but I also haven't had any flats on my tri bike/wheels/tires. My tri bike sees only 2000 road km/year, and much of that during races, where the road is at least somewhat swept.
All this to say that I've been happy with mine, but I also had a pretty good idea what to expect, and understood the pros and cons before I started using them. I also have never tried any other variety of puncture resistant tires. I would say that they are exactly as advertised; high puncture resistance and high mileage. Maybe it's a case of low expectations being exceeded.